When soft tissue such as a ligament or a tendon becomes detached from a bone, surgery may be indicated to reattach or reconstruct the tissue. Various fixation devices, including sutures, screws, staples, wedges and plugs have been used in the past to secure soft tissue to bone.
More recently, various types of suture anchors have been developed. The suture anchors are implanted in bone, and suture passed through the soft tissue is secured to the suture anchor. The technique usually requires the surgeon to tie knots in the suture, though various knotless techniques are also available.
Older style bone anchors had an external eyelet to allow the sutures to be fed through after the screw was driven into the bone. This left the eyelet exposed in the soft muscle tissue at a proximal end of the device.
Later versions of bone anchors have the sutures inserted inside the screw tip well inside the bone. This allows the outer end of the screw to stay flush with the cortical bone outer surface. The sutures can pass inside in some hollow screws from near the tip outer surface. Others have the sutures held near the tip and are exterior held between the anchor threads and the bone. In some suture anchor systems, there is a self-driving feature that has a stainless steel punch with a steel tip that can be malleted into the bone. This design leaves the tip end trapped in the bone opening meaning the patient has a small metal tip in his shoulder or knee.
Ideally, the anchor should leave no metal remnants and ideally is able to provide a knotless fixation or hold of the suture on insertion into the bone.